President Trump’s controversial nomination of Ronny L. Jackson to head the Department of Veterans Affairs has grown further complicated by the Navy physician’s pending military promotion, which he could be forced to pass up — along with an estimated $1 million in future retirement income — if confirmed for the Cabinet post.

The dual nominations and a lack of clarity from the White House have left lawmakers flummoxed about how to proceed, said a Senate aide who spoke on the condition of anonymity to offer a candid assessment of Jackson’s unusual circumstances. The situation is symptomatic of broader frustration on Capitol Hill, particularly among Senate Republicans, with the administration’s contentious personnel moves. They have complained that the time and effort required to consider multiple Cabinet nominations — the top jobs at VA, the State Department and the CIA all are pending — is an unwanted distraction during a challenging midterm election cycle.

“This whole situation is very much out of the norm,” the Senate aide said. “There’s some question here whether [Jackson’s] flag officer nomination will move forward given his VA nomination. It’s all TBD, because he can’t serve in both positions concurrently, so it wouldn’t make sense for the Senate to move the nominations concurrently.”

The timing most likely is coincidental, as the military evaluates those eligible for promotion months before their nominations are sent to Congress.

The White House did not respond to questions seeking clarity on whether it intends to deconflict Jackson’s two nominations, if the admiral has discussed his pending promotion with Trump or if it’s the president’s goal for Jackson to be promoted before he joins the Cabinet.

In an interview published over the weekend by the Avalanche-Journal in Lubbock, Tex., Jackson, a Texas native, pushed back against his critics and suggested that his military experience has prepared him for the challenges he would face leading such a sprawling and complex bureaucracy.

“I’ve been in leadership school for 23 years now,” he told the newspaper, “. . . and I’ve been able to rise to the level of an admiral, a flag officer in the Navy. I didn’t just stumble into that. So I’ve gotten a lot of leadership background, I’ve got a lot of leadership experience as a Navy officer, and I’ve got a lot of day-to-day leadership experience. You know, I’m not just an officer in the Navy; I’m an emergency medicine physician in the military. I’ve been confronted on a day-to-day basis with life-and-death decisions.

“I think I’ve got what it takes, and you know, I don’t buy into that argument at all.”

Jackson is well liked inside the White House, where he has worked for the past 12 years, and he is respected by those who know him and have been in his care. Trump is said to have marveled at Jackson’s January appearance in the White House briefing room, where he praised the president’s physical wellness and cognitive acuity. Before settling in Washington, Jackson was deployed to Iraq, where he led an emergency trauma unit responsible for treating troops grievously wounded during one of the war’s most violent stretches.

He was surprised, however, by the president’s offer to run VA, White House officials have said, and initially questioned whether, as a career Navy officer with limited managerial experience, he’s an optimal candidate to lead an agency of more than 360,000 employees.

By all accounts, “he’s an extremely sharp officer and a terrific doc,” said Barry McCaffrey, a retired Army general who served as President Bill Clinton’s drug czar. “If he retired from the military with two stars and went back to civilian life, he would have career prospects for sure. But after 12 years in the White House . . . the only qualification he has [to run VA] is the confidence of the president.

“I think it’s 50-50 he is confirmed. And if he’s confirmed, I have great empathy. Why would he succeed? The answer is: Because the president put him there.”

Jackson’s political views and his positions on key policy questions have not surfaced publicly, though he told the Avalanche-Journal that military veterans “want to know that they have access” to medical care.

“We owe the vets the absolute best care that’s available out there,” he said. It’s unclear whether Jackson was weighing in specifically on the administration’s drive to outsource more medical services. There is deepening concern among those who oppose that effort that the admiral won’t stand up to those closest to Trump who have proposed the most aggressive measures. As such, it is believed Jackson will face a difficult confirmation.

Separately, a move to VA could entail financial sacrifice. As a Cabinet secretary, Jackson would receive a salary of $210,000, though a pay freeze has the rate locked at $200,000 through the end of this year. That’s up significantly from the $150,000 he is paid as a one-star admiral and the $170,000 he would make as a two-star, according to current Defense Department pay tables. But as a senior officer living in Washington, he also rates thousands of dollars annually in housing allowance plus other special incentive pay the military makes available to medical professionals.

In the long term, a higher rank would qualify Jackson for a more generous pension, which is determined in part by a service member’s final pay grade and years of service. Assuming Jackson lives to age 90, the difference before taxes is $6.4 million vs. $5.3 million, according to estimates based on the Defense Department’s retirement pay calculator.

Specialists with First Command Financial Services, which offers financial planning and advice for the military community, independently verified these results at The Washington Post’s request but cautioned that other variables could influence Jackson’s decision-making in forgoing the promotion in favor of joining Trump’s Cabinet.

For instance, he would probably boost his future market­ability and earning power in the private sector if he can demonstrate success while running VA. Chief executives of major medical networks can command sizable salaries, and Jackson, 50, though of age to retire from the military, is at the outset of his prime earning years.

There is also the satisfaction that comes from working in service to the nation ­and for those who have sacrificed on its behalf, said Arnold Punaro, a retired Marine general who also spent many years on the staff of the Senate Armed Services Committee, overseeing, among other matters, the promotion confirmation process.